This discussion has made me revisit an old personal concept to use Liquid Nitrogen as a fuel at least for the upper stage rocket portion of the launch envelope. Water/ice cannot be made into a plasma, because it breaks down into hydrogen/Oxygen before it reaches the energy level to ionize. This means relying on just the expansion, because the resulting plasma is less than ideal for magnetic acceleration to boost Impulse, and it takes a lot of energy to turn liquid water into steam, then plasma (Water is natures' almost perfect heat sink. It guzzles energy, which is why it's so cold to us.)

Nitrogen is diatomic, and expands a useful amount in transition from liquid to gaseous states. (It's also 80% of our atmosphere by volume, so it would be the vast majority of the reaction mass during the ambient atmospheric stage.) Once you ionize it to monoatomic plasma, you have a single frequency to accelerate it, and while Cryogenic, it's also the highest temperature to liquefy it from air. And finally, it's abotu as non-toxic as you can get, so there wouldn't likely be much pollution once the ions fell back into stable diatoms. (Okay there would also be Nitroxides, Ammoniates, and Cyanic compounds from reacting with the atmosphere, but they would likely break down into safe Nitrogen before they got down to the biosphere if they passed through the Van Allen belts on the way back to the Atmosphere.)

So, you could set up a net Ramjet, cool intake air, so that the Nitrogen liquefies first, pump the remaining gasses downward to expand along with the ambient air, to keep the ground fuel fraction as low as possible, then switch to onboard tanks for the aeropause-orbit acceleration once the air runs out.

Again, probably a ground based nuclear powered Laser for the first part of the flight, vertically launched, then a LEO based satellite for tangental thrust to orbital velocity. Since the satellite is moving at orbital velocity, you'd have a short window before it overtook the craft, which would make this a high acceleration rate. Another option would be a Geosynchronous laser at a steep angle from the launch site (Over the horizon until you reached transition altitude, when it would be at a tangent to the Atmosphere.) Either way, the orbital Lase could be Solar powered, if it had enough energy capacity, and the launches were far enough apart to recharge the "Batteries" (Probably a Capacitor bank.)

Though not a true single stage, you'd have the same advantages, low launch weight, for lifting off with just an empty tank (Like the hollow prototype from the video, only probably Evacuated to lose even more wight, and draw in air from the pressure differential)and gaining energy from peripheral sources (The 2 Lasers.) I think the GSO Laser would work out the best, since it's stationary with respect to the (Equatorial) spaceport, so you don't have to worry about waiting for a launch window, and weather co-operating. Clouds would play hell with such a system.

IDK if anyone would go for it, because people would likely be as paranoid about an orbital laser as launching "Nukes" into space. of course, it's not a weapon, but it could be used as a weapon, which is more than enough for the paranoid delusionals that think the government is trying to kill us with drones, because we don't have Directed Energy implacements, and nuclear reactors in orbit, that we know of. (The Voyagers, and most of our Robotic Probes were isotope Ractor powered, but that wasn't public knowledge at the time, I met the guy who designed the one for Cassini in Los Alamos.)

_________________"You can't have everything, where would you put it?" -Steven Wright.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Good idea. In the interview Kare said probaby the [list=][/list]minimum size rocket is one with around 10kg payload. Smaller ones would be too hard to focus the beam on. But for a demo that would only need to be powered for a couple of seconds and wont be further than a couple of hundred meters from the laser could be smaller.

it is not a dumb idea this idea could be used in planetary voyages. planetery lazer rings could hit same object, the shuttle could go in place in 1 g , by that way artificial gravity could be aranged. after this accelerete faze finished, in deacalarete faze the target orbital lazer ring slow the ship till it fits the planet prbit trajectory. it could also used for space one like plane-rocket hybrid human-transporter shutles to minimize weight in rocket part. after decoupling the rocket over 10.000 mt. over the launchin lazer bays, lazer could hit the rocket till it reache low orbit, wwhen reach low orbit, orbital lazer ring continiues to accalerete the shuttle..